124 The American Geologist. August, 1894 
Selenella; a significant list even when stated in iliis brief form without 
reference to the culmination of other generic, subgeneric and specific 
types, or to the important evidence afforded by the inception, or absence 
or decline here of i\ pes distinctive both above and below. 
The lamellibranchs show series of interesting transition forms; the 
cephalopods, sparse in the earl^ stages but abundant in the later, pos- 
sess many highly distinctive genera. 
These suggestions may be taken simply as indicative of the constitu- 
tion of t In- fauna as a whole, as evidences of an individual expression 
which closer analysts would onh serve to strengthen. There are local- 
ities known wherein the fauna of each of the component stages of the 
Helderberg dwvsitm is complicated with that immediately succeeding; 
the Lower Helderberg with the Lower Oriskanj', the Lower Oriskany 
with the Upper Oriskany, and the Oriskany with the Upper Helderberg. 
So. also, there are a few places recorded (e. g., Cass county, Indiana), 
where the Upper Helderberg fauna is involved with that of the Hamil- 
ton group; more will undoubtedly he found: anything else would be 
unnatural with an uni nterrupted succession of strata and faunas. There 
is likewise, in some respects, a palpable approximation in the later 
fauna of this division, to thai of the Hamilton and typical Devonian. 
It would be surprising were there not. Who will draw the line between 
the faunas of the Cambrian and Ordovician? between the Devonian and 
( larbonif erous ? 
That the fauna of the Helderberg division is not Silurian is demon- 
strated: that it is consequently Devonian is a nonsequitur. The Devonian 
is a geological ami palaeontological entity which has never been defined. 
As it was originally simply a name for the interval bet ween the Silurian 
and Carboniferous, so it is to-day. Hut the fauna of the Helderberg di- 
vision, or the Heldekbergian, is as distinctive from that of the overlying 
Devonian as it is from the Silurian, and. as already stated, its represen- 
tation in species is quite as prolific as either of the others. The name 
proposed by the state geologists of New York has passed into desuetude. 
giving way to the procrustean adaptation of a European nomenclature 
by Europeans (Bigsby, de Verne uil, Lyell); but it is a question worthy of 
consideration whether it may not profit-ably lie revived to express a 
definite geological and biological quantity; not alone as a distinctive 
geological term, but as even more dist inct ive of a series of faunas which 
in their entirety form a body as integral and homogeneous as any other 
of the large divisions in the organic history of the Palaeozoic. It is not 
alone in New York or North America that this Helderbergian fauna is so 
clearly developed. Its correlates have been found throughout the world, 
in Belgium, France and Spain. Germany, Bohemia and Austria, Russia, 
Siberia. South Africa, Brazil and Bolivia. 
European writers have employed the term Hereynian for faunas 
equivalent in whole or part to those of the Helderberg division. The 
name is an unfortunate one. for it has never been clearly defined, has 
been applied to faunas of widely different geological age or to certain 
